Conventional types of machinery, such as various dewatering mechanisms utilized in the papermaking industry, employ vacuum dewatering systems for removing water from a substrate such as a papermaker's felt. Wear surfaces on the machinery for contact with the moving substrate take a variety of different forms. For example, on the wet end of papermaking machinery a variety of different shape foil or blade structures are employed including foils in combination with vacuum systems to dewater the substrate. Suction pipes and suction boxes, particularly wet boxes, are often used. The different types of replaceable or adjustable wear surfaces are designed to accommodate parameters involved in the system. Different factors are taken into consideration such as the nature and condition of the substrate being handled and dewatered, the type of suction system employed, and the type of wear surface or foil employed for facilitating the dewatering process.
In general, the wear surfaces are arranged in parallel position on a supporting surface interconnected with a source of vacuum. The wear surfaces, for example vacuum foils, are spaced so that elongated slots therebetween form openings for application of the vacuum. Thus, the combination of engagement with the foils and the vacuum force results in water being drawn through the slots and collected and the substrate or felt being dewatered in the desired manner.
One difficulty that occurs in utilizing the parallel arrangement of foils or wear surfaces is that the in between spaces extending the length of the elongated elements produce a loss of vacuum at the ends. This is due to several circumstances. First, the felt or substrate is not as wide as the width of the elongated foils and thus any openings at the end portions would be open to atmosphere and accordingly produce a reduction in vacuum. Second, sealing the ends is difficult in view of the fact that the slots between the wear surfaces are open ended causing introduction of air and again resulting in loss of vacuum. Accordingly, end deckles are frequently used to seal the ends of the slots between the foils and maintain a maximum vacuum condition in the central portion of the slots where the substrate travels for dewatering purposes.
The difficulty with utilizing deckles for end seals resides in the fact that the spacing between wear surfaces or foils is not a constant parameter. Dimensional variations occur in manufacture and assembly. Accordingly, mass produced deckles of generally constant dimensions are difficult to fit in slots of varied sizes. Clearly, an adjustable deckle is desirable because of the difficulty in maintaining exact blade or foil spacing in commercially mass produced products. An adjustable deckle would facilitate original manufacture of the machinery as well as field replacement.
Various types of variable width end deckles have been utilized to some degree. Adhesively bonded cushions have been used with the cushion being designed to permit compression and accordingly variation in the width of a deckle structure. Adhesives cause additional manufacturing steps and materials particularly in the application of a suitable adhesive and also present difficulties in use particularly where the adhesive fails and premature deterioration of the deckle occurs. In place of adhesively bonded compressive elements, compressive elements have been affixed to the deckle structure by means of screws or other similar fastener to avoid the difficulties present with adhesive. However, use of screws or other types of fasteners again adds to the manufacturing components and steps of assembly thus adding to the overall cost of the structure.
Accordingly, there is clearly a need for further improvement in deckle design to provide the needed adjustment for spacing purposes to accommodate for dimensional variations of wear surfaces such as blades or foils.